Treponema. The lateral arrangement is also rare. The lateral 

 monotrichous arrangement may be seen in Lachnospira and the 

 lateral multitrichous arrangement in Selenomonas. The mixed 

 arrangement is typical of Chromobacteriiim and young cultures of 

 Aeromonns. It has also been observed on several occasions, in 

 cultures physiologically related to Pseiidomoruis, and in unstable 

 mutants of various bacteria. ( See Figs. 2 and 3. ) 



Relation of Shape and Arrangement to Motility 



In a liquid medium bacteria with polar flagella as a rule move 

 more rapidly than bacteria with peritrichous flagella. The move- 

 ment of the polar flagellated bacteria is linear and smooth, while 

 that of the peritrichous flagellated bacteria is wiggly and more er- 

 ratic. The shape of the flagella may greatly affect locomotor effi- 

 ciency and will be discussed in the next section in connection with 

 flagellar variation and mutation. In media with more soHdity than 

 ordinary broth the peritrichous flagellated bacteria apparently 

 move faster than the polar flagellated bacteria. This is readily 

 demonstrated by inoculating the center of one semisolid plate with 

 a peritrichous organism such as Salmonella, and similarly inocu- 

 late another semisolid plate with a polar organism such as Pseitdo- 



FiG. 2. a, b, c, d, e, f, g. Examples of polar monotrichous flagellation, illus- 

 trating variations of wavelength. 



h. This illustrates the formation of two variants, one with a normal flagel- 

 lum and one with an undulant flagellum. 



i. A normal and a straight flagellum at the same pole. 



j, k, 1, m, n, o. Various types of polar multitrichous and lophotrichous 

 flagellation. The coiled flagella shown in o are quite rare. 



p. Subpolar monotrichous flagellation. 



q. Subpolar multitrichous flagellation. 



r. Lateral monotrichous flagellation. 



s. Lateral multitrichous flagellation. 



t, u. In t is shown a stalked organism with a flagellum at the end of the 

 stalk. In u is shown a rosette of stalked bacteria with polor monotrichous 

 flagellation. 



g,k,q. From E. Lcifson, /. Bacterial. 62, 377-389 (1951). j. From E. Leif- 

 son, Antonie van Leeuwenhoek, J. Microbiol. Serol. 20, 102-110 (1954). 

 m, o. From E. Leifson, and R. Hugh, /. Bacteriol. 65, 263-271 ( 1953). p. From 

 E. Lcifson, and E. W. Erdman, Antonie van Leeutoenhoek, J. Microbiol. Serol. 

 24, 97-110 (1958). 



10 



